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Post by dubiousgolfer on Jul 4, 2020 22:04:58 GMT -5
Dr Mann We can have infinite instantaneous variations of 'forces/torques' via the hands on the club that, when amalgamated together, can create the same 'Net Force' and 'Hand Couple' which describes the motion of the golf club.
This 'closed loop problem' makes it incredibly difficult to identify the biomechanics or even confirm its accuracy.
I think you have a huge task ahead of you to try and figure out the detailed biomechanics involved.
DG
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Post by imperfectgolfer on Jul 4, 2020 22:44:29 GMT -5
Dr Mann We can have infinite instantaneous variations of 'forces/torques' via the hands on the club that, when amalgamated together, can create the same 'Net Force' and 'Hand Couple' which describes the motion of the golf club. This 'closed loop problem' makes it incredibly difficult to identify the biomechanics or even confirm its accuracy. I think you have a huge task ahead of you to try and figure out the detailed biomechanics involved. DG I don't buy the vague "idea" that an infinite number of instantaneous forces are amalgamated together to produce a net force and a hand couple force. I believe that the net force is produced by the left hand pulling the club handle while the hand couple force is produced directly by the two hands working in an across-the-shaft manner. Jeff.
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Post by dubiousgolfer on Jul 5, 2020 8:24:28 GMT -5
I thought I'd summarise some of the information regarding 'Release' which has caused me great confusion:
PGA definition of Release: (also "let it go") generally thought of as the act of allowing the centrifugal force of the body/arms/hands/clubhead to take its course on the downswing rather than holding on or inhibiting it (can be broken down into specifics)
1. The double pendulum release according to Dave Tutelman is caused by 'Centrifugal Force' (ie. normally referred to as an inertial or pseudo/fictitious force ). By using these CF forces in equations , one can still explain the 'Release' mechanism . The same 'Release' mechanism can be mathematically explained by D'Alemberts principle using classical dynamics.
2. Jorgensen's double pendulum model had a 90 degree stopper and this caused a passive positive torque to stop the club falling into the central hub in the early downswing . Similarly, the release could be explained by both the 'Centrifugal Force' and D'Alembert principle (which is simplified mathematically into a 'Force' and 'MOF' ). The MOF element of which is responsible for the 'Release' (no positive hand couple as per PingMan).
3. Jorgensens model predicted that positive torque applied about 70 msecs before impact could create some extra clubhead speed. That if applied any earlier or later would have a negative effect on clubhead speed by impact.
4. Dave Tutelman article (which he regards as still relevant) says that it's easier for the golfer to hold onto the lag and allow it to release 100 msecs before impact to get the same extra clubhead speed as point 3 above.
5. Many 'Tour Pro' golf photos/videos show their lead wrists uncock between P5.5 and P6 (ie. but that act does not necessarily mean 'Release' as per the PGA manual).
6. Dr Kwon and SMK inverse dynamic graphs show that there is still a positive 'Hand Couple' at P5.5. In fact SMK 'Multiple Major Winner In Plane Torque' graphs still shows some residual positive hand couple after P6 (for a very small time period). It is around P6 where the MOF takes over the generation of clubhead speed in the late downswing.
7. From P5.5-P6 , 3D data systems (like Gears) show some Tour players clubhead speeds can increase significantly (ie. between 10-20 mph).
8. Do the graphs support an assumption that the golfers used in Dr Kwon and SMK 'inverse dynamic graphs' are doing what Jorgensens model predicted in point 3?
DG
It's my fault why DT has replied in the way he has . That's because I didn't phrase my questions correctly and mentioned that there was still some positive hand couple after P6 (ie. I incorrectly assumed he knew that the uncocking of the wrists happened before P6 with a positive hand couple).
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Post by imperfectgolfer on Jul 6, 2020 6:51:31 GMT -5
DG,
In your summary, you have not explained why the club starts to release around P5.5 in the driver swing of most pro golfers.
The double pendulum release model, or the D'Alembert principle, does not explain the precise timing of the release of PA#2 in "real life" pro golfers. Neither does the hand couple model explain why the release happens around P5.5 in a driver swing. That's the mystery that I would like to see solved!
The biggest problem with the hand couple theory is that is theoretically-based on inverse dynamics calculations and we do not have a series of multiple measurements on "real life" golfers that prove that it really exists. Secondly, the hand couple theorists cannot explain the golf swing biomechanics that produce the hand couple graph patterns.
Jeff.
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Post by dubiousgolfer on Jul 6, 2020 8:34:45 GMT -5
Dr Mann
"In your summary, you have not explained why the club starts to release around P5.5 in the driver swing of most pro golfers."
That's the question I am asking in point 8. Is the release around P5.5, caused by the golfer kick-starting the release with hand couple, creating a similar effect that Jorgensen found in his DP model? Where he programmed an active positive torque (equivalent of a hand couple) at the 2nd hinge joint of the DP, 70 msecs before impact, which caused an increase in clubhead speed 'over and above' a 'D'Alembert' type release.
In Jorgensen's model the hinge joints would theoretically be frictionless , but in a real golfer the timing of that positive hand-couple might have to happen earlier than 70 msec.
Or
Could that 'early' release caused by the hand couple be a 'non-optimal' biomechanical move made by golfers (even Tour Pros)?
"The biggest problem with the hand couple theory is that is theoretically-based on inverse dynamics calculations and we do not have a series of multiple measurements on "real life" golfers that prove that it really exists."
'Mathematically' the hand couple does exist but I don't think 'Sasho/DT/Kwon' would commit themselves to theorising how to create that 'mathematical image' with individual forces applied to the club via the hands. As scientists they would have to back up their theories with some proof, maybe using 'hand/club' force sensor research.
DG
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Post by dubiousgolfer on Jul 6, 2020 9:30:27 GMT -5
Some more information about Jorgensen's findings from DT's website (note the bolded part which I think is around P5.5).
----------------------------------------------------------- In fact, once he had a mathematical model that behaved like the golf swing, he ran some "what if" analyses to see whether application of wrist torque could add to power. He found that there is a critical time about 70-100 milliseconds before impact (where the arms are 60º before the impact position) where torque changes from hurting clubhead speed to helping it. That is, any uncocking wrist torque before the critical time will reduce clubhead speed at impact. You can indeed increase clubhead speed a bit by applying wrist torque, but only if you can do it for just the last 70 milliseconds before impact, and not before.
Jorgensen's book is a bit more optimistic. In his chapter 4, some of the points he makes are: It is always a bad idea to apply positive torque early in the downswing. It is always a bad idea to apply positive torque throughout the downswing. (We knew that already from Rod White.) It is generally helpful to apply negative torque (that is, hold the lag angle, retard release) throughout the downswing. (Also Rod White.) What is new and interesting is his analysis of adding positive torque late in the downswing: "Let us look at such a helping action of the wrists late in the downswing. Extensive calculations with the standard swing modified by a constant helping torque of 2 ft-lbs by the wrists late in the downswing show that indeed such a helping torque does produce an increase in clubhead speed at impact. The maximum increase in clubhead speed at impact comes with the torque starting about seven hundredths of a second before the ball is hit. The resulting clubhead speed was found to be only about 0.7% greater than that of the standard swing. This constant torque acting for a longer time or for a shorter time at the end of the downswing produces clubhead speeds less than the maximum." In other words, there is room for a properly executed push or slap to increase power. But it is not much of an increase, and it has to be timed very precisely. Not extremely promising, but not a closed door either. -----------------------
Its a pity that Jorgensen didn't add a larger 'helping torque' in his model rather than interested in the effect of muscular 'wrist torque' . In SMK's video the 'multiple major winner ' golfer is applying around 52N force (per hand) at around P5.5, which is about 11.7 lbs force. Just wondering how that would affect the clubhead speed if timed 70 msecs before impact?
DG
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Post by imperfectgolfer on Jul 6, 2020 19:16:29 GMT -5
DG, I do not know what "Kick-starts" the release of PA#2 between P5.2 => P5.5 in most pro golfers and it could be a passive phenomenon. Look at these kinematic sequences of multiple pro golfers. Look at Rory McIlroy's, Rickie Fowler's, JB Holmes' and Grant Waite's kinematic graphs. Note that the slope of the clubhead speed graph is the same as the slope of the left arm speed graph in the early-mid downswing to about P5. Then the slope of the clubhead speed graph does not increase between P5 and impact. Interestingly, the left arm speed reaches its peak speed after the clubhead speed graph separates from the left arm speed graph and that happens at about P5.5.
Interestingly, the release of PA#2, which we know starts to happen in most pro golfers between P5.2/P5.5, does not affect the slope of the clubhead speed graph. There is no evidence that there is any PA#2 releasing "force" (or torque) in play that makes the clubshaft accelerate faster and the slope of the clubhead speed graph is seemingly determined in the early downswing between P4 and P5/P5.2 and it is highly correlated with the speed of left arm motion (speed of release of PA#4). Jeff.
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Post by dubiousgolfer on Jul 6, 2020 20:54:12 GMT -5
Dr Mann From SMK's 'Multiple Major Winner In Plane Torques Graphs' , at P5.5 the hand couple force I've estimated in each hand would be 131N (which is 29lbs force approx) and then reduces to 52N (11.7 lbs force approx) at P6 when the MOF starts to take over. This rapidly reducing hand couple between P5.5-P6 happened in 20 msecs and I don't know whether that is enough time to produce any significant increase in the angular acceleration of the club. P5.5P6Note that at P5.5 the clubhead speed was 74.3 mph and by the time it reached P6 (when the 'hand couple' and MOF graphs crossed over) it had reached 90.4 mph . I don't know what percentage of that 16mph increase in clubhead speed was caused by: 1. The Hand Couple 2. The 'Linear Force' (applied along the hand path). 3. The MOF (which was also in the positive part of the graph when it crossed with the hand couple graph). If we knew the angular velocity of the club at P5.5 and compared the angular velocity at P6 we could then make some approximation as to the effect of the hand couple. In my opinion 50% of any increase in the angular acceleration could be attributed to the 'hand couple' because the MOF has also crept into the positive side of the graph from P5.5 (and would also be contributing to some of the increase in clubhead angular acceleration). DG
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Post by dubiousgolfer on Jul 7, 2020 6:39:22 GMT -5
Dr Mann
I am now almost convinced that the golfer is applying hand couple to assist MOF force (as it moves from zero to positive ) to kick-start release. Look at the P5.5 frame image in my previous post and the time slot before impact. It is 0.071 secs before impact and seems too coincidental that it almost matches Jorgensen's findings about applying wrist torque at 70msecs before impact.
Is it also a coincidence that it seems to correlate with the timing for maximum Net Torque (red line graph) too?
DG
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Post by imperfectgolfer on Jul 7, 2020 9:09:12 GMT -5
DG, You wrote-: " From SMK's 'Multiple Major Winner In Plane Torques Graphs' , at P5.5 the hand couple force I've estimated in each hand would be 131N (which is 29lbs force approx) and then reduces to 52N (11.7 lbs force approx) at P6 when the MOF starts to take over. This rapidly reducing hand couple between P5.5-P6 happened in 20 msecs and I don't know whether that is enough time to produce any significant increase in the angular acceleration of the club." However, the angular acceleration of the club does not increase around the P5.5 time point. The slope of the clubhead speed graph is unchanged from the early downswing all the way to impact in those kinematic graphs that I posted and there is no increase in the steepness of the slope of the clubhead speed graph at ~P5.5.
You also wrote: "I am now almost convinced that the golfer is applying hand couple to assist MOF force (as it moves from zero to positive ) to kick-start release. Look at the P5.5 frame image in my previous post and the time slot before impact. It is 0.071 secs before impact and seems too coincidental that it almost matches Jorgensen's findings about applying wrist torque at 70msecs before impact."
If the hand couple is providing a "kick-start" force to induce the release of PA#2, why does it not occur earlier than P5.5 when the hand couple torque is even larger in magnitude?
Jeff.
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Post by dubiousgolfer on Jul 7, 2020 11:12:53 GMT -5
Dr Mann
In my opinion those graphs do not provide enough detailed granularity to show the effect of any clubhead angular acceleration (for the 20 milliseconds approx being used to uncock lead wrist).
The 'kick -start' hand couple only seems to work to increase the overall clubhead angular velocity 'at impact' when applied specifically at 70 msecs before impact.
Jorgensen found that if you applied positive wrist torque earlier or later than 70 msecs (before impact), it would cause a decrease in clubhead speed 'at impact'.
I know this sounds a bit simplistic but it almost seems analogues to pushing a child on a swing where you add a bit of impetus just as the swing transitions into the downswing.
Anyhow , I thought you might be interested in Dave Tutelmans reply to my questions (I didn't use TGM terms which might cause him confusion).
------------------------------------------------- DG :Question 1 Most Tour Pro golfer photo images/videos show their lead wrists uncock _before_ shaft horizontal in the downswing? Many of them start uncocking their lead wrist between shaft vertical and shaft horizontal in the downswing.
DT Reply: True! For the big hitters, it looks to me like about 70° instead of the nominal wrist cock of 90°. Not sure the 90° is correct for the biggest hitters, though.
DG Question 2. The graphs I previously sent to you in .pdf attachments show a positive hand couple _before_ shaft horizontal
DT Reply: Possible.
DG Question 3. Doesn't this mean that the_hand couple is responsible for the uncocking of the lead wrist before shaft horizontal_? The MOF doesn't seem to be involved in any uncocking of the lead wrist _before_ shaft horizontal (if it did, it would seem to be very small).
DT Reply: Probably true if so. If the wrist cock were still 90°, that would be passive torque for the hand couple. It might still be passive torque, because the best golfers let their wrist go into flexion in this vicinity of the swing, which reduces the range of motion for wrist cock. But I'm not at all sure of that.
(Feel free to view that as my pushing my agenda. I haven't done the homework to KNOW that.)
DG Question 4: When I read your article 'What Powers The Golf Swing' there was mention of Jorgensen's model where he found golfers could be applying an 'assist' positive couple around 70 msecs before impact to increase clubhead speed. You mentioned that it would take quite a coordinated golfer to perform that move and inferred it was easier to hold the lag and then allow passive CF induced release around 100 msecs. I was therefore wondering if most Tour Pro golfers are actually doing what Jorgensen's model predicted at 70 msecs before impact? Is it something they've naturally ingrained in their swing techniques?
DT Reply: I really doubt it, but there is a possibility.
But let's get to where my doubts are coming from about positive couple adding to clubhead speed at impact. I've got two (admittedly older, and analytic rather than experimental) sources.
(1) Jorgensen. The analysis in his book, aimed at the double pendulum model, showed that a NEGATIVE couple throughout the downswing was productive. Why? Because it delayed the release until the rotation was faster, meaning that more moment of force was applied later. And, once things are rotating fast, moment of force is much more productive than hand torque. Yes, it's an old model, and 2D. But I don't see anything invalid about that part of the math. I've used a slightly newer (but still 2D) model that showed the same thing.
(2) Sasho MacKenzie. (https://people.stfx.ca/smackenz/Publications/MacKenzie%202009%20A%20three%20dimensional%20forward%20dynamics%20model%20of%20the%20golf%20swing.pdf) This is a forward-dynamic model, rather than the reverse-dynamic model we've been talking about. He turns a mathematical model loose (including some human limitations like torque-speed curves and muscle strength limits) to optimize clubhead speed. If you look at the contribution of wrist torque, it is very small compared with the other torques. Also, its contribution occurs earlier in the downswing, at left arm horizontal rather than shaft horizontal. What does that tell me? That the BEST that a mathematical model can do has very minimal contribution from wrist torque. Some action items for me (but probably not this week; more important irons in the fire):
(a) Try to compute the contribution of the wrist torque in Sasho's forward dynamic analysis.
(b) Ask Sasho if the model included NEGATIVE wrist torque as a possibility. (If not, we might well have seen that, too.)
------------------------------------------
DG
PS. This reply was received before I noticed the hand couple being applied at the 0.071 sec time slot in SMK's video (when Net Torque was maximum and MOF just passing the zero line).
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Post by imperfectgolfer on Jul 7, 2020 11:29:07 GMT -5
DG,
It is interesting to read DT's answers to your questions.
He seemingly is very uncertain as to whether a hand couple phenomenon is in play in terms of increasing the efficiency of release of PA#2. He also suggests that SMK's positive wrist torque (based on his forward dynamics model) is being applied at P5 and not at P5.5 (70 msec before impact).
I would be interested in seeing SMK and Dr. Kwon answer the same questions that you posed to DT.
The timing of the release of PA#2 is still a "mystery" to me, and I find the D'Alembert principle's explanation and SMK's hand couple/MoF explanation unsatisfactory/incomplete.
Jeff.
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Post by dubiousgolfer on Jul 7, 2020 12:24:16 GMT -5
Dr Mann
You have some valid qualms about SMK hand couple/MOF explanation . D'Alemberts principle is just a mathematical explanation to explain the concept of 'Release' using classical dynamics.
If I recall, SMK validates his inverse dynamics on his forward dynamics model. I don't know whether his forward dynamics model 100% reflects a real golfers swing and I suspect there will always be some error, maybe enough to question the accuracy of his inverse dynamics graphs at the millisecond granularity level.
I think DT's 'agenda' could be to promote an idea of negative torque in the early phases of the downswing until Mof takes over the role.
DT
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Post by dubiousgolfer on Jul 8, 2020 7:14:36 GMT -5
Dr Mann
Is what DT said anatomically correct?
"It might still be passive torque, because the best golfers let their wrist go into flexion in this vicinity of the swing, which reduces the range of motion for wrist cock. But I'm not at all sure of that."
DG
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Post by imperfectgolfer on Jul 8, 2020 13:59:28 GMT -5
Dr Mann Is what DT said anatomically correct? "It might still be passive torque, because the best golfers let their wrist go into flexion in this vicinity of the swing, which reduces the range of motion for wrist cock. But I'm not at all sure of that."DG It is true that the wrist cannot radially deviate as much when the left wrist is bowed, but it can still ulnar deviate easily, so I cannot understand why he believes that left wrist bowing near P5.5 may affect the release of PA#2. Jeff.
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